Development and Function of Natural Autoreactive B Cells

描述(由申请人提供)：尽管人们普遍接受具有自我反应的B细胞被删除或功能不活跃，但在健康动物的血清中仍可发现被称为“天然自身抗体”的自我反应性抗体。这种天然自身抗体是由一小部分独特表达细胞表面糖蛋白CD5的B细胞产生的。与成人骨髓相比，这些CD5+自体反应性B细胞更多地来自胎儿B细胞前体细胞，作为B-1 B细胞发育的一部分。我们的研究探索了为什么这种自然的自体反应性B细胞应该存在，它们发展的机制，以及它们调节失调的可能性。通过建立和研究表达天然抗Thy-1自身抗体(ATA)的小鼠自然自身反应性B细胞模型，我们发现自身抗原对于CD5+ATA自身反应性B-1B细胞的聚集是重要的，并且B细胞受体(BCR)信号强度相对较高，介导了阳性选择过程。相反，在传统的B细胞发育过程中，来自骨髓的脾细胞(B-2)表达相同的bcr的细胞发生负选择。在这次更新中，我们将对B细胞亚群的发育机制有一个全面的了解。我们将首先研究传统的非自身反应性B-2B细胞成熟的机制，特别是由其他淋巴细胞提供的非BCR信号的意义。我们将评估T细胞和胎儿B-1B细胞在成人B-2(滤泡B细胞)发育和免疫中的作用及其潜在的相互作用(目标1)。为了了解为什么自体反应性B-1阳性选择与胎儿B细胞发育有关，我们将确定一个“胎儿B-1信号”，我们假设它反映了独特的细胞机制，决定了与骨髓(B-2)发育相比，BCR信号阈值的不同。为了追踪早期产生的B-1细胞的命运，我们将培育Lysmd2-GFP报告小鼠，基于我们最近发现的该基因是胎儿B-1信号的成员(目标2)。完成所提出的工作将极大地促进我们对自身反应性B-1阳性选择和B细胞发育的总体理解。我们假设，早期产生的天然自身反应性淋巴细胞是出于关键的保护原因，作为先天性免疫系统的一个组成部分，以帮助随后的适应性免疫系统的发展。7.与公共卫生的相关性 在某些自身免疫的小鼠品系中，随着年龄的增长，CD5+B细胞会发生异常扩张， 和B淋巴瘤。在人类中，CD5的表达是慢性B组晚期发展的标志 细胞性白血病(B CLL)，占美国成人白血病病例的三分之一， 西欧。全面了解B细胞的发育、选择、 和成熟机制(S)，以及建立CD5+自然自身反应性B细胞是如何 在本申请中提出的正常调节和功能对于 为这种失调的CD5+B细胞设计合理的疗法。

DESCRIPTION (provided by applicant): Although it is widely accepted that B cells with self-reactivity are deleted or rendered functionally inactive, self-reactive antibodies, referred to as "natural autoantibodies" can be found in the serum of healthy animals. Such natural autoantibodies are produced by a small fraction of B cells with distinctive expression of the cell surface glycoprotein CD5. These CD5+ autoreactive B cells are more frequently generated from fetal B cell precursors as a part of "B-1" B cell development than those in the adult bone marrow. Our research explores why such natural autoreactive B cells should exist, the mechanism whereby they develop, and their potential for dysregulation. By establishing and investigating mouse natural autoreactive B cell models expressing natural anti-Thy-1 autoantibody (ATA), we found that self-antigen is important for CD5+ ATA autoreactive B-1 B cell accumulation with relatively higher B cell receptor (BCR) signal intensity mediating a positive selection process. In contrast, negative selection occurs for cells expressing the identical BCR during conventional B cell development ("B-2") in spleen from bone marrow. In this renewal, we will obtain a comprehensive understanding of the mechanism for B cell subset development. We will first investigate the mechanism of conventional non-autoreactive B-2 B cell maturation, in particular the significance of non-BCR signaling provided by other lymphocytes. We will assess the role of T cells and fetal B-1 B cells in adult B-2 (follicular B cell) development and immunity and their potential interaction (Aim 1). To understand why autoreactive B-1 positive selection occurs in relation to fetal B cell development, we will identify a "fetal B-1 signature" that we hypothesize reflects distinctive cellular machinery determining a difference in BCR signaling threshold, compared to bone marrow (B-2) development. To follow early-generated B-1 cell fate, we will produce Lysmd2-GFP reporter mice, based on our recent identification of this gene as a member of the fetal B-1 signature (Aim 2). Accomplishing the proposed work will significantly advance our understanding of autoreactive B-1 positive selection and B cell development in general. We hypothesize that early generation of natural autoreactive lymphocytes occurs for critical protective reasons, as a component of the innate immune system, to help development of the adaptive immune systems that follows. 7. Relevance to Public Health Abnormal expansions of CD5+ B cells can occur with age, in certain autoimmune mouse strains, and as B lymphomas. In humans, CD5 expression is a hallmark of late developing chronic B cell leukemia (B CLL), accounting for a third of adult leukemia cases in the United States and Western Europe. Arriving at a comprehensive understanding of B cell development, selection, and maturation mechanism(s), and establishing how CD5+ natural autoreactive B cell are normally regulated and function, as proposed in this application, will be critically important for designing rational therapies of such dysregulated CD5+ B cells.